Dynamic Interactions of Eye and Head Movements During Reading with Single Vision and Progressive Lenses

Abstract

Abstract: : Purpose: We have reported (ARVO, 2001) that progressive addition lenses (PALs) produced an increase in the frequency and amplitude of compensatory head movements during reading at an intermediate working distance when compared with single vision lenses (SVL). In the present study, dynamic interactions of the eye and head movements of the same subjects under the same conditions were assessed. Methods: Horizontal eye and head movements were recorded objectively and simultaneously at a rate of 60 Hz during reading of single (SP; 14 deg H) and double (DP; 37deg H) page paragraphs at 60 cm with binocular viewing. Subjects were comprised of 11 visually-normal, presbyopic individuals ages 45 to 71 years selected from the clinic patient population. Reading was performed with 3 types of spectacle lenses: a single vision lens (SVL), PAL-I with a relatively wide intermediate zone (7.85mm; 18 deg H), and PAL-II with a relatively narrow intermediate zone (5.60mm; 13deg H). Testing was conducted under normal diffuse fluorescent overhead illumination (47 cd/m₂). Results: 1). For SP, eye movements were initiated before head movements, and for DP, the reverse was found, for all 3 lenses. 2). With the PAL-II, head movements were completed before eye movements were completed, and the reverse was found with the PAL-I and SVL, for both SP and DP. 3). With the PAL-II, gaze stabilization time was longer than with SVL and PAL-I, for both SP and DP. Conclusions: Eye and head movement strategies and timing were contingent upon viewing conditions. With PAL-II, eye movements were completed after head movements were completed, which suggested that additional eye movements were required to locate the clear vision zone. In addition, gaze stabilization was achieved later with the PAL-II and its narrow intermediate zone. These may be factors for the reduced reading rate and related symptoms reported by PAL wearers. The dynamic interactions of eye and head movements during reading with the PALs appear to be a sensitive indicator of lens optical design parameters on overall reading performance, as they can discriminate between PALs designs as well as between SVLs and PALs. Supported by The Spectacle Lens Group of Johnson & Johnson Vision Care, Inc.

Keywords: 406 eye movements